In known treatment of cancerous lesions in the human body irradiation of the disordered tissue, such as a tumor, is used in order to destroy the disordered tissue. The disordered tissue may be placed in all parts of the body. When the disordered tissue is positioned in some parts it may be difficult to irradiate without crucially damaging other essential parts of the body and in some cases the irradiation has caused irreversible damage.
In order to avert such damage the irradiation of the disordered tissue is executed by radiating the disordered tissue from different angles, so that the surrounding healthy tissue is only subjected to an irradiation, the effect of which being curable over a short period of time. Thus, the irradiation is not crucially damaging the surrounding healthy tissue. However, the disordered tissue is irradiated from various selected angles in order to destroy it.
Thus, the irradiation of the disordered tissue is restricted by the amount of irradiation, which healthy tissue may tolerate without being crucially or irreversible damaged. This limitation of the irradiation is further increased by the fact that it may be difficult to precisely locate the disordered tissue and to determinate the extension of the disordered tissue inside the body.
U.S. Pat. No. 5,853,366 describes a solution to this problem. The location of the tumor is performed by inserting at least three markers in relevant positions around the periphery of the tumor. These markers are made from stainless steel capable of being detected in a conventional X-ray image of the body in order to position the irradiation source in relation to the tumor before irradiation of the tumor. Each marker is depicted as one point in an X-ray image. These markers are inserted directly into the tissue surrounding the tumor and the markers are barbed or V-shaped in order to securely fasten the markers into the tissue thereby inhibit movement of the markers. Subsequently to positioning of the markers and irradiation of the tumor, the barbed markers have to be removed by invasive surgery.
WO 99/27839 discloses a system for positioning and repositioning of a portion of a patient's body with respect to a treatment or imaging machine including multiple cameras to view the body and the machine. Index markers placed externally on the patient's body, either light-emitting, passive, geometric shapes, or natural landmarks, are identified and located by the cameras in 3D space. Anatomical targets determined from image scanning can be located relative to reference positions associated with the treatment or diagnostic machine. Several forms of camera, index markers, methods and systems accommodate different clinical uses. X-ray imaging of the patient further refines anatomical target positioning relative to the treatment or diagnostic imaging reference point. Movements of the patient based on comparative analysis of imaging determined anatomical targets relative to reference points on treatment or diagnostic apparatus are controlled by the system and process.
WO 02/19908 discloses a method and an apparatus for compensating for breathing and other motions of the patient during treatment, the method comprising: generating images of the target region prior to the treatment; periodically generating positional data about the internal target region based on markers implanted in the patient's body; continuously generating positional data about external motion of the patient's body using one or more external sensors; and generating a correspondence between the position of the internal target region and the external sensors so that the treatment is directed towards the position of the target region of the patient based on the positional data of the external sensors. The target region's position is subsequently matched to the position of the target region in the preoperative images.
WO 02/100485 discloses a system and method for accurately locating and tracking the position of a target, such as a tumor or the like, within a body. In one embodiment, the system includes one or more excitable beacons positioned in or near the target, an external excitation source that remotely excites the beacons to produce an identifiable signal, and a plurality of sensors spaced apart in a known geometry relative to each other. A computer is coupled to the sensors and configured to use the beacon signals to identify a target isocenter within the target. The computer compares the position of the target isocenter with the location of the treatment isocenter. The computer also controls movement of the patient and a patient support device so the target isocenter is coincident with the treatment isocenter before and during radiation therapy.
Even though markers as described above are used to define the extent of the disordered tissue area, the whole area may be difficult to view in the image. For this reason and other reasons when planning the irradiation of the disordered tissue, the medical practitioner or the attending physician plans the irradiation by applying an irradiation margin in order to be sure that all of the disordered tissue area is irradiated. This margin results in some of the healthy tissue being deliberately irradiated and therefore the aforementioned crucial damages may occur. In this respect the irradiation is planned being divided into several irradiation sequences. Also, only fiducial markers are disclosed. A fiducial marker itself provides no possibility of identifying any rotation of the marker. Fiducial markers provide no possibility of localizing the disordered tissue without having at least two, and as disclosed, preferably three fiducial markers employed.
Further reasons for applying the irradiation margin is the inaccuracy in positioning the patient below the irradiation equipment, the inaccuracy of the resolution of the derived image of the disordered tissue and the fact that the internal organs may move over time. Such movement of the internal organs may be caused by respiration and/or by day-to-day movements. The use of implanted markers for guiding the treatment as described above can, to some extend, improve the accuracy of the positioning of the patient.
One method of positioning the patient before treatment is by making an image of the area in which the disordered tissue to be irradiated is located, and the patient is moved in relation to the irradiation equipment by locating the bone structure of the patient in relation to which bone structure the disordered tissue is located in the pre-examination image. The location of bone structure has shown to introduce some of the aforementioned inaccuracy.
Additionally, movement of the disordered tissue to be irradiated between the first pre-examination image and the subsequent image for setting up the irradiation equipment before irradiating the disordered tissue is an indefinable movement. The extent of movement caused by respiration may vary up to 10 cm. The movement caused by respiration varies substantially from one person to another.
Some attempts have been made in order to record the movement caused by the respiration. The movement pattern is entered into the control of the irradiation equipment during the irradiation of the tumor. This additional process of defining a movement pattern is expensive and time consuming, and due to the fact that the respiration of a nervous person, a person suffering from Parkinson's Disease or a person suffering from Cerebral Paralysis is asymptotic, the recorded pattern has often shown to be asynchronous with the present respiration. The recording of a movement pattern may therefore not provide a complete accuracy of the irradiation of the tumor.
An additional solution is known from http://www.elekta.com/healthcareinternational.nsf/pga_Frameset?openpage&url=umc_demonstrates_automatic_marker_detection_with_a-si (“Elekta”) disclosing a better detection of the markers using a template of the markers.
Therefore, an improved method of guiding the irradiation equipment is needed in order to at least partly overcome the aforementioned disadvantages of the prior art relating to adjusting the irradiation equipment. An improved method of treating disordered tissue, such as a tumor, may also be needed in order to at least partly overcome the aforementioned disadvantages of the prior art relating to therapy.
U.S. Pat. No. 6,307,914 discloses a moving body pursuit irradiating device comprising a linac for irradiating a medical treatment beam to a tumor, and a tumor marker buried in the vicinity of the tumor, a first X-ray fluoroscope for picking up an image of said tumor marker from a first direction, and a second X-ray fluoroscope for picking up the image of said tumor marker from a second direction at the same time as said first X-ray fluoroscope, first and second recognition processing sections which execute template matching at a real time level at a predetermined frame rate by a shading normalization mutual correlation method for applying a template image of the tumor marker registered in advance to image information digitized by said first and second image input sections, and calculate first and second two-dimensional coordinates of said tumor marker, a central arithmetic processing section for calculating three-dimensional coordinates of said tumor marker from the first and second two-dimensional coordinates calculated by said first and second recognition processing sections; and an irradiating control section for controlling the irradiation of the medical treatment beam of said linac by said calculated three-dimensional coordinates of the tumor marker.
Implanted markers of prior art that is positioned in the body of the patient are buried in the tissue and therefore require invasive surgery to be inserted in the body as well as further subsequent invasive surgery to be retracted from the body.
Diagnostic images made with different imaging technologies and with different medical imaging equipment are derived with a time interval between the images, and with the patient repositioned on a different couch for each image. This results in different set-up conditions for each image. The different set-up conditions result in a difference between the actual position of the tissue of interest inside the body of the patient in the different images, compared to visually clear objects in the images, placed a distance from the tissue of interest, such as bone structures, outer surface of the patient's body etc. The difference between the positions of the tissue of interest in the different images can occur either by internal organ motion inside the patient's body and/or by inaccurate positioning of the patient below the medical imaging equipment.
Therefore, an improved method of collating different images by different medical imaging equipment is needed in order to at least partly overcome the aforementioned disadvantages of the prior art relating to localizing the tissue of interest.